Self-recycling actuator and valve incorporating it

ABSTRACT

A self-recycling actuator operated by a source of fluid pressure is used to control the operation of a valve. The valve has a main valve member whose position is controlled by a pilot valve adapted to vent the high pressure side of the main valve member. The self-recycling actuator controls the pilot valve and is operated by the high pressure fluid from the inlet of the main valve. High pressure fluid brought to the inlet of the selfrecycling actuator displaces a plunger member thereby opening the pilot valve and hence the main valve. At the same time, high pressure fluid enters a recycling chamber. As pressure builds up in the recycling chamber, the plunger is returned to its initial position. Vent means reduces the pressure in the recycling chamber thereby initiating a new cycle.

ited States Patent Otto 1 June 6, 1972 s41 SELF-RECYCLING ACTUATOR AND2,947,323 8/1960 Becker 1 37/624. 14

VALVE INCORPORATING IT Primary Examiner-Alan Cohan [72] Inventor. NoelA. Otto, Whlppany, NJ. Atmmey Breitenfe!d & Levine [73] Assignee:Automatic Switch Co. [22] Filed: Mar. 19, 1970 [57] ABSTRACT I Aself-recycling actuator operated by a source of fluid pres- [21] Appl24316 sure is used to control the operation of a valve. The valve has amain valve member whose position is controlled by a pilot -S- Cl -l4,1/52, 91/416 valve adapted to vent the high pressure side of the mainvalve f Cl t t t F16k 31/335 member. The self-recycling actuatorcontrols the pilot valve Fleld of Search 1 l4, l 6, and is operated thepressure from the inlet of the 91/ 5 2 main valve. High pressure fluidbrought to the inlet of the selfa recycling actuator displaces a plungermember thereby open- [56] References cued ing the pilot valve and hencethe main valve. At the same time, UNITED STATES PATENTS high pressurefluid enters a recycling chamber. As pressure builds up m the recyclingchamber, the plunger 15 returned to Matthews l X its positio m ventmeans reduces the pressure in the 3,216,328 1 1/1965 Peterson l 37/624.14 X recycling chamber thereby initiating a new 1 3,509,901 5/1970Hollibaugh 137/624. 14 X 3 3,083,732 4/1963 Becker 137/624. 14 9 Claim,6 Drawing Figures PATENTEDJUH 61972 SHEET 10F 3 l I CI I FIG 2 FIG!INVENTORI A/OEL 4- 0770 BY ATTORNEYS PATENYEDJUN 6 1912 3, 667, 502

SHEET 2 OF 3 FIG. 3

INVENTORI i Q I ATTORNEYS PATENTEDJW 5 973 3, 667, 502 sum 3 BF 3lNVENTOR.

I ATTORNEYS SELF-RECYCLING ACTUATOR AND VALVE INCORPORATING IT Thisinvention relates to a self-recycling actuator for use with a valve, andto a pilot operated valve incorporating the actuator. The invention isparticularly useful in connection with pneumatic valves adapted tocontrol air flow and be controlled by air pressure. However, it is to beunderstood that the actuator and valve have utility with fluidsgenerally.

There are numerous installations including valves which must be operatedperiodically. Such cycling of the valves in ordinarily controlled byelectric, pneumatic, or hydraulic timing devices.

It is an objectof the present invention to provide a selfrecyclingactuator for a valve which accomplishes periodic cycling of theassociated valve without the use of expensive and cumbersome timingequipment and associated wiring. Such a valve finds usefulness in a vastrange of industrial applications, since the valve can be readilyinstalled in fluid systems without requiring additional auxiliaryequipment to control the cycling of the valve.

A feature of the invention involves the fact that the selfrecyclingactuator may be incorporated in a valve to provide a unitaryself-recycling valve requiring only the continued presence of fluidpressure at the inlet of the valve to accomplish both the timing of thesuccessive valve actuations, and the production of an actuating force tocontrol the valve.

Another feature of the invention involves the fact that the recyclingactuator can easily be adjusted to vary the cycle period of the valvefrom fractions of a second to many minutes.

Additional features and advantages of the invention will be apparentfrom the following description in which reference is made to theaccompanying drawings:

In the drawings:

FIG. 1 is a longitudinal cross-sectional view of a valve according tothis invention showing the main and pilot valves, and the self-recyclingactuator,.in closed position;

FIG. 2 is a fragmentary cross-sectional view of a portion of theself-recycling actuator looking in a direction opposite to the directionof viewing in FIG.1;

FIG. 3 is a view similar to FIG. 1, showing the main and pilot valves;and the self-recycling actuator in open position;

FIG; 4 is an enlarged cross-sectional view of the upper part of FIG. 1,showing the self-recycling actuator;

FIG. 5 is a cross-sectional view of another embodiment of aself-recycling actuator, according to this invention, employing adiaphragm, and

FIG. 6 is a cross-sectional view, of another embodiment of aself-recycling actuator, according to this invention, having twodiaphragms.

The valve 10 chosen to illustrate this invention and shown in FIGS. l-4,includes a valve body comprising sections 11, and 12, and an end cap oractuator housing 13 all of which are fastened together by bolts 14extending through all of the sections and threaded into main section 11.Bolts 14 also secure a retaining piece 15 to the top of end cap 13.

Body section 11 is formed with an inlet port 19, an outlet port 20, bothadapted for connection to conduits, an orifice 21 between these twoports, and a valve seat 22 surrounding the orifice. A diaphragm 23formed of a suitable flexible and resilient material, such as rubber,extends above the orifice 21, the margin of the diaphragm beingsandwiched between the body sections 1 l and 12. A main valve member 24carried by the diaphragm 23 is movable into and out of engagement withthe valve seat 22 to close and open the main valve, respectively.

Above diaphragm 23 is a chamber 27 communicating with the inlet port 19via a small hole 28 in diaphragm 23. Within chamber 27 is a compressionspring 29 seated at its lower end upon valve member 24, and at its upperend against the flange portion of a pilot valve spring seat member 30.Spring 29 I presses the flange portion of member 30 against the top wall31 of chamber 27. When chamber 27 is filled with fluid at the inletpressure, the fluid force against the upper face of diaphragm 23combined with the force of spring 29 keeps valve member 24 upon seat 22and closes the main valve, as shown in FIG. 1. If the pressure inchamber 27 is relieved, the inlet pressure acting on the lower face ofdiaphragm 23 lifts the diaphragm and valve member (FIG. 3) and the mainvalve remains open as long as the pressure in chamber 27 remainsrelatively low.

The pressure in chamber 27 is controlled by a pilot valve, to bedescribed now. A large bore 33 extends upwardly from the top wall 31 ofchamber 27, and a smaller bore 34 extends upwardly from the top wall ofbore 33. The area of the bore 33 top wall surrounding bore 34 serves asa pilot valve seat 32. A lateral bore 35 extends between bore 34, at apoint above seat 32, and a vent opening at the exterior surface of bodysection 12, which opens into a low pressure region such as the atmosphere.

A pilot valve member 36 within bore 33 is movable toward and away fromvalve seat 32 to close and open the pilot valve, respectively, i.e., toprevent and establish, respectively, communication between chamber 27and the vent opening at the outer end of bore 35, via hole 39 in member30, and bores 33 and 34. Within bore 33 is a compression spring 37seated at its upper end against pilot valve member 36 and at its lowerend against member 30. A stem 38 is slidably arranged within bore 34,the upper end of the stem having a diameter slightly smaller than thediameter of bore 34, and the lower end of the stem having a reduceddiameter to permit free communication through bore 34 between bore 33and bore 35.

When chamber 27 is filled with fluid at the inlet pressure, the fluidforce against the lower face of pilot valve 36 combined with the forceof spring 37 keeps valve member 36 upon seat 32 and closes the pilotvalve, as shown in FIG. 1. If stem 38 is shifted downwardly (FIG. 3),pilot valve member 36 is pushed away from seat 32, against the force ofspring 37 and the fluid force, thereby opening the pilot valve, andallowing the fluid above diaphragm 23 to rush out of chamber 27 throughbores 33, 34, and 35, thereby permitting the main valve member 24 toopen.

The positioning of pilot valve stem 38 is controlled by theself-recycling actuator, to be described now. Passages 41 and 42 invalve body sections 11 and 12 respectively effect communication betweeninlet port 19 and an orifice 43 surrounded by a valve seat 44 formed atthe top of valve body section 12. A diaphragm 40, the margin of which issandwiched between body section 12 and end cap 13, is held against valveseat 44 by a compression spring 45, The lower end of spring 45 is seatedwithin a cup 46 bearing against the upper face of diaphragm 40, and theregion above diaphragm 40 is open to the atmosphere through hole 47.

When the pressure of the fluid in passage 42 exerts a force on diaphragm40 great enough to overcome the force exerted by spring 45, diaphragm 40is lifted off valve seat 44 (FIG. 3) and the fluid in passage 42 flowsinto annular region 51 and thence through passages 52, 53, 54 and 55, inthe valve body section 12 and end cap 13, to the inlet orifice 56 of theactuator.

The pressure fluid entering through orifice 56 exerts a downward forceon a valve disc 60 in the end of a plunger 61 sufficient to drive valvedisc 60 off a valve seat 62 surrounding orifice 56. As a result, highpressure fluid enters the upper portion of a plunger chamber 63 definedby a bore 76 in end cap 13, and exerts a downward force, against theentire upper force against upper surface 64 of plunger 61, the fluid inplunger chamber 63 passes through radial passage 68, axial passage 69,and radial passages 70 in plunger 61 into a recycling chamber 71.Recycling chamber 71 is defined by a bore 77 in end cap 13, below andlarger than bore 76, and cavities in the upper surface of valve bodysection 12, these cavities and bore 77 communicating through openings 66at the lower end of the wall of bore 77. Seal ring 72 held in place byretaining member 73 prevents leakage from recycling chamber 71 tochamber 27, around valve stem 38. Upper and lower seal rings 74 and 75carried by plunger 61 prevent leakage from plunger chamber 63 and fromrecycling chamber 71. The portion of bore 77 between seal rings 74 and75 is vented to the atmosphere by passage 78.

As can be easily seen in FIGS. 1, 3, and 4, the area of lower surface 65of plunger 61 plus the area of the exposed lower surface of seal 75, issubstantially larger than the area of upper end surface 64 of plunger 61plus the area of the exposed upper surface of seal 74. Therefore, oncethe pressures in plunger chamber 63 and recycling chamber 71 haveequalized, because of the flow through the plunger passageways 68, 69,and 70, there will be a net upward force exerted on the plunger 61forcing it upwardly in the plunger chamber until the plunger disc 60contacts the valve seat 62 thereby closing the plunger chamber 63 andpreventing any more high pressure fluid from entering chambers 63 and71.

Recycling chamber 71 is vented to the atmosphere through a bleed deviceinthe top of end cap 13. A hole 80 in end cap 13 establishescommunication between chamber 71 and the atmosphere. An adjustable stem81, having a conical point 82 arranged in hole 80, is threadablypositioned in a fixed nut 83. Rotation of stem 81 causes longitudinalmovement of conical point 82 to vary the size of the flow path throughhole 80, and therefore the rate at which the fluid in recycling chamber71 is vented to the atmosphere.

As the venting through hole 80 takes place, the pressure in recyclingchamber 71 drops until the force remaining in the recycling chamber 71is insufficient to overcome the force of high pressure fluid exerted onvalve disc 60 in the upper end of plunger 61. When this occurs, theforce exerted by the pressure fluid in passage 55 again forces plunger61 down a small distance sufficient to disengage valve disc 60 fromvalve seat 62 allowing the pressure fluid to reenter plunger chamber 63,thereby initiating a new cycle.

In order to insure proper operation of the self-recycling actuator, itis desirable to provide a means by which the fluid in the recyclingchamber 71 can at some predetermined pressure by quickly vented, torapidly reduce the remaining pressure in the chamber and insure positiveaction of the plunger 61 in moving downward in plunger chamber 63 toopen inlet orifice 56. To accomplish this purpose, a preset low pressurerelief device, shown in FIG. 2, is carried by the end cap 13. A hollowcylindrical projection 91 extends downward into recycling chamber 71from the lower surface of end cap 13. A hollow valve seat member 93,having a central passage 98, is located within projection 91, the lowerend of member 93 defining a valve seat 94. A valve disc 90 is adapted tocooperate with valve seat 94 to close passage 98 though which recyclingchamber 71 can otherwise communicate with the atmosphere. When the disc90 is unseated, it rests upon an abutment 95 carried by projection 91. Acompression spring 92 surrounds member 93, and is seated at its upperend against a shoulder 97 presented by member 93, and at its lower endagainst disc 90. Retaining piece 15 maintains member 93 withinprojection 91, and has a hole 96 aligned with passage 98.

When the pressure in recycling chamber 71 is high the upward forceexerted on disc 90 is sufficient to overcome the bias of compressionspring 92, whereby valve disc 90 is pressed against seat 94 therebypreventing any venting of recycling chamber 71 through passages 98 and96. However, as the fluid in recycling chamber 71 is vented through thehole 80 of the adjustable bleed device, the force urging valve disc 90against seat 94 decreases and at some point is no longer able toovercome the force exerted by the compression spring 92. As a result,the valve disc 90 is moved away from seat 94,

by the spring, allowing a rapid venting of any of the pressure fluidremaining in the recycling chamber 71. Passage 98 is such a largeopening to the atmosphere, as compared to bleed vent hole 80, that anyleakage of high pressure fluid into recycling chamber 71 will not causeany significant build up of pressure, and hence downward movement ofplunger 61 is assured.

FIGS. 5 and 6 show alternative embodiments of the selfrecyclingactuator. In the embodiment shown in FIG. 5, parts comparable to partsof FIG. 4 bear the same reference numerals followed by a prime. Passages53 and 54 in housing 13' carry high pressure fluid to orifice 56'. Thepressure fluid exerts a force against valve disc 60 which moves plunger61 down a distance sufficient to disengage valve disc 60' from valveseat 62' to allow pressure fluid to enter plunger chamber 63' and exerta force on the entire upper surface 64' of the plunger to drive thelatter downward. A diaphragm 102 is secured at its margins between bodysection 12 and cap 13'. A bearing plate 103 is secured to the center ofdiaphragm 102, and to the lower end of plunger 61'. Downward movement ofthe plunger therefore causes the diaphragm to push stem 38 downwardly.

Internal passages 104 and 105 in the housing 13' and body section 12,respectively, establish communication between plunger chamber 63' andrecycling chamber 71 Seal ring 74' and diaphragm 102 prevent leakagefrom plunger chamber 63 and recycling chamber 71, respectively to thespace between the sealing devices, which is vented through passage 78'.Venting of recycling chamber 71' is accomplished by means not shown.Comparable to those described above with respect to FIGS. l-4.

Except for the difference in the structure of the plunger and thepassages through which the plunger chamber and the recycling chambercommunicate, the embodiment of the recycling actuator shown in FIG. 5functions identically with the embodiment shown in FIG. 4. Thedifferencein the surface area between the lower surface of disphragm 102 and theupper surface 64 of plunger 61 produces a net force which tends to seatplunger disc 60' against seat 62 when the pressure in plunger chamber 63and recycling chamber 71' are equal.

The embodiment of the self-recycling actuator shown in FIG. 6 isidentical to that shown in FIG. 5 with the exception of the plungerconstruction and the sealing means used to prevent leakage from theplunger chamber and the recycling chamber. Parts comparable to parts ofFIGS. 4 and 5 bear the same reference numerals followed by a doubleprime. The most significant difference between FIGS. 5 and 6 isdiaphragm used in place of seal 74' to prevent leakage from plungerchamber 63". The region 111 between disphragms 110 and 102' is ventedthrough passage 78". Because of the use of the additional diaphragm theactuator housing is formed of two parts 13a and 13b which sandwich themargin of disphragm 110 between them. Additionally, because of the useof diaphragm 110, the plunger is fabricated in three parts. Upper part112 and lower part 113 sandwich the diaphragm between them, and a bolt 114 secures parts 1 12 and 113 together. Passages 104' 115, and 105"carry the pressurized fluid from plunger chamber 63" to recyclingchamber 71". Since the area of the bottom face of diaphragm 102" islarger than the area of the top surfaces of plunger part 112 anddiaphragm 110, plunger-disc 60" seats against seat 62" when thepressures in chambers 63" and 71" are equal.

It will be appreciated that the period of each cycle of operation of theactuator, and hence the valve, can be adjusted by rotating stem 81 toreduce or enlarge the flow path through hole 80. Specifically, enlargingthe flow path allows fluid in recycling chamber to vent more quickly andhence increases the number of cycles per unit time. Reducing the flowpath reduces the number of cycles per unit time.

It should be pointed out, that the low pressure cut off valve includingdiaphragm 40, in the passage between the inlet port 19 and the inletorifice 56 of the self-recycling actuator is not necessary for thefunctioning of the apparatus, nor is the rapid vent device for therecirculating chamber, shown in FIG. 2. The arrangement illustratedwould be capable of operating effectively without either of theseelements. Furthermore, although for simplicity the above descriptionrefers to various portions of the valve and actuator communicating withthe atmosphere, it is to be understood that the atmosphere is intendedto mean any relatively low pressure region.

The invention has been shown and described in preferred form only, andby way of example, and many variations may be made in the inventionwhich will still be comprised within its spirit. It is understood,therefore, that the invention is not limited to any specific form orembodiment except insofar as such limitations are included in theappended claims.

What is claimed is:

l. A self-recycling actuator comprising:

a. a housing having a plunger chamber and a recycling chamber,

b. means establishing communication between said chambers,

c. an inlet through which high pressure fluid may enter said plungerchamber,

(1. vent means through which fluid may leave said recycling chamber at arate slower than the rate at which fluid enters said plunger chamberwhen said inlet is open,

e. closure means movable within said plunger chamber for closing andopening said inlet, and

f. means within said recycling chamber operatively associated with saidclosure means and responsive to fluid pressure in said recycling chamberof at least a certain minimum value for moving said closure means to aposition in which the latter closes said inlet,

whereby said means (f) causes said closure means (e) to maintain saidinlet (c) closed until sufficient fluid bleeds out of said recyclingchamber through vent means (d) to reduce the pressure in said recyclingchamber enough to permit the high pressure fluid at said inlet (c) tomove said closure means (e) and open said inlet thereby allowing highpressure fluid to once again fill said plunger and recycling chambers,

said vent means (d) including low pressure relief means comprising anorifice communicating with said recycling chamber, a valve memberoperatively associated with said orifice to close said orifice inresponse to positive pressure in said recycling chamber, and biasingmeans to urge said valve member to the open position, whereby when thepressure in said recycling chamber drops below a predetermined value,the bias on said valve member opens said orifice and allows rapidventing of the pressure in said recycling chamber.

2. A self-recycling actuator as defined in claim 1 wherein said closuremeans (e) and means (f) form parts of a plunger extending between saidplunger and recycling chambers, the end of said plunger located withinsaid plunger chamber having a cross-sectional area smaller than the endof said plunger located within said recycling chamber.

3. A self-recycling actuator as'defined in claim 1 wherein said means(f) includes a diaphragm, one face of said diaphragm being exposed tothe pressure within said recycling chamber.

4. A self-recycling actuator as defined in claim 3 wherein said closuremeans (e) includes a plunger, one end of which is located within saidplunger chambers, and the other end of which is operatively associatedwith the other face of said diaphragm.

5. A self-recycling actuator as defined in claim 3 wherein said closuremeans (e) includes a second diaphragm, one face of said second diaphragmbeing exposed to the pressure within said plunger chamber.

6. A valve comprising:

g. a valve body having an inlet port, an outlet port, and an orificebetween said ports surrounded by a valve seat, h. a main valve membermovable into and out of engagement with said valve seat to close andopen the valve, respectively,

i. a chamber on the side of said valve member opposite said valve seat,said chamber communicating with said inlet port, whereby inlet pressureis applied to said opposite side of said valve member to keep the valveclosed,

j. a vent opening in said body,

k. a pilot valve carried by said body establishing communication betweensaid chamber and said vent opening, whereby when said pilot valve isopened the pressure in said chamber is released and the valve ispermitted to open, and

l. a self-recycling actuator as defined in claim 1, for controlling theoperation of said pilot valve.

7. A valve as defined in claim 6 wherein said means (f) is operativelyassociated with said pilot valve (k) for opening the latter in responseto movement of said closure means (e) in a direction which causes saidinlet (c) to open.

8. A valve as defined in claim 7 including a part extending between saidpilot valve (k) and said recycling chamber, said part transmittingmovement of said means (f) to said pilot valve.

9. A self-recycling actuator comprising:

a. a housing having a plunger chamber and a recycling chamber,

b. means establishing communication between said chambers, an inletthrough which high pressure fluid may enter said plunger chamber, ventmeans through which fluid may leave said recycling chamber at a rateslower than the rate at which fluid enters said plunger chamber whensaid inlet is open,

e. closure means movable within said plunger chamber for closing andopening said inlet,

f. means within said recycling chamber operatively associated with saidclosure means and responsive to fluid pressure in said recycling chamberof at least a certain minimum value for moving said closure means to aposition in which the latter closes said inlet,

whereby said means (f) causes said closure means (e) to maintain saidinlet (c) closed until sufficient fluid bleeds out of said recyclingchamber through vent means (d) to reduce the pressure in said recyclingchamber enough to permit the high pressure fluid at said inlet (c) tomove said closure means (e) and open said inlet thereby allowing highpressure fluid to once again fill said plunger and recycling chambers,

g. conduit means for bringing high pressure fluid to said inlet, and

h. valve means within said conduit means for closing the latter in theabsence of a predetermined minimum pressure in said conduit means.

1. A self-recycling actuator comprising: a. a housing having a plungerchamber and a recycling chamber, b. means establishing communicationbetween said chambers, c. an inlet through which high pressure fluid mayenter said plunger chamber, d. vent means through which fluid may leavesaid recycling chamber at a rate slower than the rate at which fluidenters said plunger chamber when said inlet is open, e. closure meansmovable within said plunger chamber for closing and opening said inlet,and f. means within said recycling chamber operatively associated withsaid closure means and responsive to fluid pressure in said recyclingchamber of at least a certain minimum value for moving said closuremeans to a position in which the latter closes said inlet, whereby saidmeans (f) causes said closure means (e) to maintain said inlet (c)closed until sufficient fluid bleeds out of said recycling chamberthrough vent means (d) to reduce the pressure in said recycling chambErenough to permit the high pressure fluid at said inlet (c) to move saidclosure means (e) and open said inlet thereby allowing high pressurefluid to once again fill said plunger and recycling chambers, said ventmeans (d) including low pressure relief means comprising an orificecommunicating with said recycling chamber, a valve member operativelyassociated with said orifice to close said orifice in response topositive pressure in said recycling chamber, and biasing means to urgesaid valve member to the open position, whereby when the pressure insaid recycling chamber drops below a predetermined value, the bias onsaid valve member opens said orifice and allows rapid venting of thepressure in said recycling chamber.
 2. A self-recycling actuator asdefined in claim 1 wherein said closure means (e) and means (f) formparts of a plunger extending between said plunger and recyclingchambers, the end of said plunger located within said plunger chamberhaving a cross-sectional area smaller than the end of said plungerlocated within said recycling chamber.
 4. A self-recycling actuator asdefined in claim 3 wherein said closure means (e) includes a plunger,one end of which is located within said plunger chambers, and the otherend of which is operatively associated with the other face of saiddiaphragm.
 5. A self-recycling actuator as defined in claim 3 whereinsaid closure means (e) includes a second diaphragm, one face of saidsecond diaphragm being exposed to the pressure within said plungerchamber.
 6. A valve comprising: g. a valve body having an inlet port, anoutlet port, and an orifice between said ports surrounded by a valveseat, h. a main valve member movable into and out of engagement withsaid valve seat to close and open the valve, respectively, i. a chamberon the side of said valve member opposite said valve seat, said chambercommunicating with said inlet port, whereby inlet pressure is applied tosaid opposite side of said valve member to keep the valve closed, j. avent opening in said body, k. a pilot valve carried by said bodyestablishing communication between said chamber and said vent opening,whereby when said pilot valve is opened the pressure in said chamber isreleased and the valve is permitted to open, and l. a self-recyclingactuator as defined in claim 1, for controlling the operation of saidpilot valve.
 7. A valve as defined in claim 6 wherein said means (f) isoperatively associated with said pilot valve (k) for opening the latterin response to movement of said closure means (e) in a direction whichcauses said inlet (c) to open.
 8. A valve as defined in claim 7including a part extending between said pilot valve (k) and saidrecycling chamber, said part transmitting movement of said means (f) tosaid pilot valve.
 9. A self-recycling actuator comprising: a. a housinghaving a plunger chamber and a recycling chamber, b. means establishingcommunication between said chambers, c. an inlet through which highpressure fluid may enter said plunger chamber, d. vent means throughwhich fluid may leave said recycling chamber at a rate slower than therate at which fluid enters said plunger chamber when said inlet is open,e. closure means movable within said plunger chamber for closing andopening said inlet, f. means within said recycling chamber operativelyassociated with said closure means and responsive to fluid pressure insaid recycling chamber of at least a certain minimum value for movingsaid closure means to a position in which the latter closes said inlet,whereby said means (f) causes said closure means (e) to maintain saidinlet (c) closed until sufficient fluid bleeds out of said recyclingchamber through vent means (d) to reduce the pressure In said recyclingchamber enough to permit the high pressure fluid at said inlet (c) tomove said closure means (e) and open said inlet thereby allowing highpressure fluid to once again fill said plunger and recycling chambers,g. conduit means for bringing high pressure fluid to said inlet, and h.valve means within said conduit means for closing the latter in theabsence of a predetermined minimum pressure in said conduit means.
 13. Aself-recycling actuator as defined in claim 1 wherein said means (f)includes a diaphragm, one face of said diaphragm being exposed to thepressure within said recycling chamber.